[Clang][Sanitizers] Check '++', '--' and _Complex subscripts as accesses

-fsanitize=array-bounds allows an index one past the end of an array
when only the address of the element is formed ('&a[i]'), but not when
the element is read or written. Whether a subscript is an access was
only determined by EmitCheckedLValue and by the scalar and aggregate
loads, and only for a bare subscript. Everywhere else the subscript was
emitted through EmitLValue, which treats it as forming an address, so
these accesses one past the end went undetected:

  int a[4];
  a[i]++; --a[i];            // also on '_Atomic' and 'counted_by' arrays
  (a[i]) = 1; (a[i])++;      // parenthesized subscripts
  _Complex double c[4];
  c[i]++; c[i] += 1.0; c[i] = 1.0; x = c[i]; x = __real__ c[i];

Add EmitAccessedLValue, which emits an array subscript (looking through
parentheses) as an access when the bounds check is enabled, and use it
for the operands of '++' and '--', for '_Complex' loads, stores and
compound assignments, for the operand of '__real__'/'__imag__' (whose
result, like a member, only exists if the element does), and in
EmitCheckedLValue.

Assisted-by: Claude Opus 5.5